Various techniques for utilizing grains having a high silver chloride content, i.e., so-called high silver chloride grains (grains having a silver chloride content of 80% or more, hereinafter referred to as "high silver chloride grains"), have been proposed for the purpose of simple and rapid development processing. The use of high silver chloride grains brings about such advantages as developing speed is increased and reusability of a processing solution is heightened. Therefore, materials of the types in which high silver chloride grains are used have now become the mainstream of photosensitive materials for printing such as color photographic paper. In the present invention, processing time means the time from the initiation of processing (contact of a photographic material with a developing solution) to drying (Dry to Dry).
High silver chloride grains according to ordinary manufacturing conditions are liable to become grains having {100} outer faces (hereinafter referred to as {100} grains), and grains so far been used practically are also cubic grains. Tabular {100} grains having a large specific surface area (the ratio of a surface area to a volume) have been developed in recent years, which have various advantages such as spectral sensitization can be performed effectively, and the covering power after development is large by virtue of the large specific surface area. Examples of such grains are disclosed in U.S. Pat. Nos. 5,320,938, 5,264,337 and 5,292,632.
However, as compared with conventionally used silver bromide grains, high silver chloride {100} grains have a problem such as grains are easily fogged. To cope with this problem, grains having a high silver chloride content and {111} faces as outer faces (hereinafter referred to as {111} grains), have been utilized. An example thereof is disclosed in JP-A-6-138619 (the term "JP-A" as used herein means an "unexamined published Japanese patent application").
Special contrivances are necessary to manufacture {111} grains having a high silver chloride content. Wey discloses in U.S. Pat. No. 4,399,215 a method of manufacturing high silver chloride tabular grains by using ammonia. The fact that ammonia is used in the grains manufactured according to this method means that silver chloride grains originally having high solubility is produced with higher solubility, therefore, practicable small size grains are difficult to be produced. Further, such grains have a disadvantage of fogging being liable to occur as the pH at manufacturing time is as high as from 8 to 10. Maskasky discloses in U.S. Pat. No. 5,061,617 high silver chloride {111} grains manufactured by the use of thiocyanate. Thiocyanate also increases the solubility of silver chloride so with ammonia. For forming high silver chloride grains having {111} outer faces without increasing the solubility, methods by the addition of additives (crystal phase controllers, i.e., crystal habit controllers) at the time of grain formation are known. Examples of such methods are listed below.
______________________________________ Patent No. Crystal Habit Controller Inventor ______________________________________ U.S. Pat. No. 4,400,463 Azaindenes plus Maskasky thioether peptizer U.S. Pat. No. 4,783,398 2,4-Dithiazolidinone Mifune et al. U.S. Pat. No. 4,713,323 Aminopyrazolopyrimidine Maskasky U.S. Pat. No. 4,983,508 Bispyridinium salt Ishiguro et al. U.S. Pat. No. 5,185,239 Triaminopyrimidine Maskasky U.S. Pat. No. 5,178,997 7-Azaindole compound Maskasky U.S. Pat. No. 5,178,998 Xanthine Maskasky JP-A-64-70741 Dye Nishikawa et al. JP-A-3-212639 Aminothioether Ishiguro JP-A-4-283742 Thiourea derivative Ishiguro JP-A-4-335632 Triazolium salt Ishiguro JP-A-2-32 Bispyridinium salt Ishiguro et al. JP-A-8-227117 Monopyridinium salt Ozeki et al. ______________________________________
Further, the tabular grains are preferred for the spectral sensitization since the tabular grains have a large surface area to a volume (i.e., specific surface area) and therefore can adsorb a large amount of sensitizing dyes. However, in use of the tabular grains, a large residual color is generated after processing, and thereby the residual color is observed as fog. Accordingly, the problem regarding generation of fog becomes more serious as compared with the regular grains.
On the other hand, the color developing time of 180 seconds has now become the mainstream in color printing materials. Further shortening of the processing time is desired, but when the processing time is shortened, the amount of the sensitizing dye used in the emulsion remained after development (residual color) is increased and the problem of the residual color is serious the more. Accordingly, techniques for reducing the fog attributable to residual colors have been demanded.
A technique for improving this problem as to high silver chloride {100} tabular grains is disclosed in U.S. Patent 5,674,674, but the technique for inhibiting the fog resulting from a residual color with respect to high silver chloride {111} tabular grains has also been desired.